Stan's suggestion is a LOT cheaper (those adapters are extremely handy to have around), but MTH also makes an adapter cable TIU/Barrel Jack Adapter Cable as another option (and may be readily available). The bad part is the $10.95 MSRP.
I got some of the adapters Stan posted and used them myself (after also buying an MTH adapter a few years ago). I suppose there is nothing wrong with cutting the cord, but I am a fan of leaving the barrel jack in place and not cutting the cord, just personal preference. Either way, be sure to check phasing as Susan pointed out above.